Are You Good at Mowing Lawns?
I don’t know what sort of neurodiverse bucket this puts me in, but I think a lot about mowing the lawn1 relative to how much time I actually spend mowing lawns (~6-7 hours per year). And so I was completely fascinated by The Pudding’s latest post on optimal lawn mowing paths and “why some people mow a lawn better than others”.
They built several digital lawns for people to mow and recorded all of their moves, how often they paused at certain times, and who mowed an optimal path.
Solving the lawn mowing problem is formally called Coverage Path Planning, and is related to one of the most famous path planning problems in computer science: The Traveling Salesman Problem.
Humans turn out to be pretty good mowers, especially those who take their time and have played some video games (including, one would assume, Dig Dug, Pac-Man, Mr. Do!, and any other game where you need to worry about dead-ends).
Sarah, one of the best mowers, spent her attention unevenly on purpose. She had a theory about why.
“The bigger spaces have more cognitive load for you to figure out what the best path is. Whereas the smaller spaces…there are fewer decisions to make.”
She planned the tight, trap-prone sections carefully and winged it on the open ones.
So it’s not about thinking more or faster, but when thinking happens. That’s what a good heuristic does: it spends your attention on the decisions that matter and nothing on the ones that don’t.
The piece is interactive so you get to try your hand at digital mowing as well.
My actual lawn is very irregularly shaped with a few dead-ends & choke points and an added wrinkle that I can’t blow grass clippings into the flower beds (so I can only go one-way the “wrong way” in those areas). So every time I mow, I’m trying to figure out the optimal path so I don’t end up backtracking too much. I probably end up saving about 45 seconds of actual time but boy is it fun from an intellectual standpoint.
See my post on Tidying Up from more than 20 years ago. ↩
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These are my favorite kinds of thought experiments — low stakes but deeply satisfying even thrilling to excel at. (In a similar vein, I plan travel routes among errands far longer than I spend actually running errands)
But having now played the (fun!) Pudding piece, I find the discomfort of stopping in the middle of the lawn or in a dead end completely overriding my efficiency calc — irl I’d still have to back track to the garage, so is that really most efficient?
I play a game on my phone called “It’s literally just mowing”. Apparently you can become President of the Mowing Association but my aspirations are not so lofty. I just mow the lawns with Gump-like zen.
Definitely just downloaded this :)
Oh man, this gets my messenger brain firing. I used to spend so much time thinking about the optimal route for the 8 or 9 or 10 packages I was holding. It froze me sometimes on busy days and I had to just tell myself, JUST START RIDING YOUR BIKE. The act of putting myself into motion seemed to start sorting my optimal route in a less panicky way.
Are good mowers also good dishwasher loaders? The packing problem is also NP Complete after all.
Me: "Ooh if I just re-arrange everything I can fit this sieve in too"
Friend: "I swear I could have washed the whole load in the sink by now"
🤓
I naturally turned to the comments to see if anyone has thought about this: in real life, unless you are using a ride-on mower, you have to pay an effort "cost" when turning, expecially when making 180 degrees turns.
This is to say I like the post as an initial peek into the problem, but I need more to finally crack my optimal lawn path riddle.
Oh Yes! 90 turns are much less taxing than 180s. Elevations matter too (says someone who has twice bought a house on a hill 🙃)
The Pudding's model also does not take into account stinging insects, which I have encountered more than once in my loops 'round the yard.
I use a reel mower and frequently backtrack due to missed / pushed grass. I don’t mind the inefficiency; it’s quiet & meditative. (Also I have a pretty small lawn.)
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